<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
<script type="text/javascript">
	str = 'abcdEFG';

	alert(str.toUpperCase());	//转成大写
	alert(str.toLowerCase());	//转成小写
</script>
</body>
</html>